At the clinical level at the LAC-USC Medical Center we are seeing relatively large numbers of young patients with cerebral vascular changes which we believe are secondary to drug abuse. In almost all of these patients, the histories were unreliable or not available regarding the specific drugs taken, combination of drugs, dosages, impurities in the drugs, etc. We want first to determine which specific drugs or combinations of drugs are producing the vascular changes. Secondly, we would like to evaluate where possible all the pertinent related variables such as dosages, impurities, methods of administration, role of anoxia, etc. Thirdly, we would like to determine the mechanism of these vascular injuries and finally, we would like to evaluate possible therapeutic regimes for minimizing the resulting brain damage wherever such is possible. We have initiated an experimental drug abuse investigation, using the Rhesus monkey and the Simonsen-Albino rat. We plan a series of studies using these animals, to evaluate the effects of amphetamine (I.V. and oral), barbituates (I.V. and oral), and oral marihuana. The doses of these drugs will approximate doses being used by the human drug abuse population. Primary investigative techniques will be cerebral angiography and histopathology.